A processor may be used in many applications where the processing components are subject to intense heat and radiation. For example, a missile may carry a processor that operates at high temperatures, or a satellite may carry a processor that operates in a high radiation environment (e.g., solar protons or cosmic rays). However, heat and radiation may degrade or damage these processing components. Processors based on semiconducting materials, such as silicon, silicon-germanium, gallium arsenide, or gallium nitride, are particularly vulnerable to high heat and radiation. Consequently, these processors require heavy shielding and expensive cooling systems. Vacuum microelectronic devices are immune to these pernicious operating conditions and are thus more suitable for such operating environments. However, vacuum microelectronics have suffered from relatively high operating voltages and eventual failure due to cold cathode tip erosion.